1. Field of the Invention
The present invention concerns a shift mechanism for a motor vehicle with at least one input shaft as well as an output shaft and a plurality of gears arranged on the shafts, which can be brought into and out of engagement by means of an actuator.
2. Description of the Related Art
Transmissions for motor vehicles are already known in many executions. On the basis of the cost advantage of manually shifted transmissions, by which the driver determines the gear change, such manual transmissions have been and are still applied broadly. In addition, automatic transmissions have also become known, by which in the field of passenger cars fully automated shift mechanisms with a hydrodynamic converter and a coupled planetary transmission have become important. On account of the torque converter there is in such transmissions no direct connection between the vehicle and the engine with its braking force, so that such automatic transmissions are often provided with a parking lock, by which it allows securing the vehicle against unintentional rolling movement. In those known automatic transmissions the locking process is actuated by the driver of the vehicle, in which he moves the shift lever into the parking position P, which through an actuation mechanism in the form of for example pull or push rods, results in blocking of the output shaft of the transmission.
Based on the cost advantage of manual transmissions as described above and despite it, the existing tendency for increased comfort in motor vehicles, automated shift mechanisms have already become known, by which an actuator in the form for example of an electric motor or two electric motors relieves the driver of the burden of the selection process and the gear change process. Also in a motor vehicle with an automated shift mechanism a safeguard is desirable against unintentional rolling movement of the vehicle on the ground of the resulting danger of accidents.
An object of the invention is therefore based on providing a shift mechanism for a motor vehicle, which safely prevents unintentional movement of the vehicle.
In accordance with the invention, to solve that problem a shift mechanism is provided having at least one input shaft as well as an output shaft, and a plurality of gears arranged on the shafts and which can be brought into and out of engagement by means of an actuator, and including a parking lock device that is actuated by the actuator to block the output shaft. Advantageous improvements of the shift mechanism are retained in the dependent claims.
In accordance with the invention a shift mechanism for a motor vehicle is provided with at least one input shaft as well as at least one output shaft, and a multitude of gears arranged on shafts, which can be engaged and disengaged by means of an actuator, whereby the actuator can also be utilized to actuate a parking lock device to block the output shaft of the transmission. That is, in other words, a shift mechanism in accordance with the invention, by which the selection process and the shifting process for shifting gears is caused by an actuator in the form of, for example, one or more electric motors, a parking lock device is provided for blocking the output shaft of the transmission, and the parking lock device is also activated by the actuator for the shift mechanism, therefore, for example, the transmission shifter, and it can be moved into a parking lock position and also disengaged from it again. The actuator can thereby activate the parking lock device, for example by an activation device provided between the parking lock device and the actuator.
The parking lock device can be a parking lock gear mounted non-rotatably on a transmission shaft and a pawl that can be engaged therewith, which through a pre-stressed spring element can be releasably brought into engagement with the parking lock gear. The pre-stressed spring element actuated by the actuator serves to bring the transmission into the parking lock position by the pawl and the parking lock gear, when upon parking of the motor vehicle a direct tooth-to-tooth position exists, thus when parking the vehicle there is no engagement of the pawl in the parking lock gear. A minute movement of the motor vehicle then leads to a rotation of the parking lock gear relative to the pawl that is under tension from the pre-stressed spring element, so that the pawl tooth after that brief relative movement engages with the gear tooth of the parking lock gear and thereby brings about the parking lock position of the shift mechanism in accordance with the invention.
In accordance with a further embodiment the parking lock can also be an interconnected shift coupling that is actuated by a pre-stressed spring element and is provided in the drive train of a motor vehicle, and by means of which the output side portion of the drive train that is coupled with the transmission output shaft can be blocked. The shift coupling can be arranged in the output side portion of the drive train after the transmission. Such a construction then is advantageous, for example, when the transmission is in the form of a hybrid transmission, that is, with an available electric motor coupled with and in addition to the internal-combustion engine, which can also operate as a generator and thereby carry out a starter-generator function. One such electric motor can then also be utilized to start the internal-combustion engine, whereby for that purpose the drive train after the transmission output shaft must be disengaged by the shift coupling. The electric motor can also be installed to deliver torque to the drive train, or for recuperation during the braking of the motor vehicle. One or more shift couplings can also be provided in the drive train near the shift coupling for carrying out the parking lock function for disconnecting the drive train. The shift coupling for the parking lock function can also be installed to engage and disengage the drive train, so that both functions, namely the parking lock function and the engaging and disengaging of the drive train, can be carried out by only one shift coupling. Thereby the actuator is utilized for the shifting process in the transmission as well as for the actuation of the parking lock shift coupling for the parking lock function, and in the case of one or more additional shift couplings it is also utilized to actuate those couplings so that only one actuator is necessary.
To bring about a parking lock function the actuator provided on the shift mechanism can actuate a spring element, which on its side actuates the shift coupling which is provided in the drive train to disengage the drive train of the motor vehicle, and by that means it can block the output side portion of the drive train that is coupled with the transmission output shaft, in which the shift coupling serves for example to block the output side portion of the drive train against the transmission housing.
Therewith, to assure a secure engagement position at the tooth-to-tooth condition of the pawl to the parking lock gear described previously, or also at both interconnected shift coupling halves, the invention provides for securing them in position by the actuator and/or the actuating mechanism, in which the spring element is in a prestressed position. When the actuator is provided in the form of an electric motor for example, it will no longer be energized after parking the motor vehicle, to conserve the power supply of the vehicle, so that it no longer actively actuates the spring element. By fixing the actuator in the position where it pre-stresses the spring element, provision is made for the pre-stress of the spring element to prevent the disengagement of the actuator from its position that corresponds with the parking lock position of the shift mechanism. For that purpose the actuator can actuate the spring element, for example through an irreversible gear step, for example a worm gear drive, whereby, however, the actuator and/or the actuating mechanism is also locked by means of a stop in which the pre-stressed spring element can be secured. That stop can for example be formed similar to a stop notch of a central selector shaft. It is also possible to secure the actuator and/or the actuation mechanism by means of a load moment lock in which the spring element is in its pre-stressed position. Also when the spring element is in its pre-stressed position, the actuator can still carry out adjustment operations in the drive train of the motor vehicle and/or in the transmission.
In accordance with the invention it is thereby provided that the shift mechanism is an automatic transmission, or one provided with a load-shifting clutch and a shiftable transmission without interruption of the pulling force, or also a hybrid transmission, as has already been described.
In accordance with a further embodiment the shift mechanism is distinguished in that the mechanism is only shiftable into the parking lock position when all shift rods or other shift elements of the transmission are in the neutral position. Hereby it is assured that no conflicting condition can occur in such a way that the transmission would be, for example, in the forward driving position in first gear and the actuator would actuate the pawl or the shift clutch, which would lead to a sudden stoppage of the transmission output shaft, although the driver of the motor vehicle is considering moving in first gear.
It is also provided, after reaching the parking lock position, to shift the transmission into a neutral position, which can also be formed by an additional neutral path. Moreover, a wide shift fork opening can be provided, for example, so that in a transmission with a central selector shaft a selector finger can engage the shift fork opening of the shift rod, which actuates the pawl or the shift coupling, so that the parking lock position of the transmission will be brought about, and thereafter disengagement of the shift finger from the wide shift fork opening is brought about without thereby canceling the parking lock position. This is, by way of example, advantageous when the internal-combustion engine of the motor vehicle can only be started in a neutral position and otherwise the service brake of the motor vehicle would have to be activated to start the engine.
It is also provided that the transmission can be shifted into the forward driving position or the backing-up driving position after achieving the parking lock position. Shifting into the forward driving position, that is, for example, into first gear with the parking lock activated, the parking lock position can, for example, be utilized to prevent the vehicle from rolling backwards during a short duration stop on an inclined road, and for further forward and uphill travel of the motor vehicle the first gear is already engaged, whereby the drive clutch is disengaged and then the actuator serves to release the parking lock position and simultaneously engages the drive clutch, so that it is possible to start uphill without rolling backwards.
In accordance with the invention it is provided that the actuator available for carrying out the shift operations of the transmission, that is, by way of example, the transmission actuator, also is included to actuate one or more clutches provided in the drive train of the motor vehicle. It is thereby advantageous, by way of example, when a hybrid drive is installed, in which an electric motor is provided near the internal-combustion engine, that serves to start the internal-combustion engine, and that also is included as a generator for the provision of electrical potential to the power supply of the motor vehicle and provides for recuperation during braking of the motor vehicle, and it also can provide torque to the drive train of the motor vehicle. By that arrangement the electric motor operates on the transmission input shaft as well as the drive shaft, as well as on the transmission output shaft, so that two clutches are provided, that, by way of example, can be interconnected shift clutches, which are actuated by the actuator. When the one or more additional shift clutches are actuated by the actuator through an actuation mechanism, they can be arranged in an engaged or disengaged position of the one or more shift clutches. The actuator can also be drawn upon to perform additional adjustment procedures in the engaged or disengaged position, such as, by way of example, the actuation of additional shift couplings that are available in the drive train, or also for shift operations in the shift mechanism. The actuation mechanism for the one or more shift couplings can, by way of example, be arranged as an irreversible gear stage similar to the actuation mechanism for the parking lock device, a stop, or a load-moment lock. The actuator is therefore utilized in the adjustment procedures in the shift mechanism, for the actuation of the parking lock device, and/or for the actuation of one or more shift clutches in the drive train of the motor vehicle.